Although smoking during pregnancy has previously been associated with a higher risk of miscarriage, premature birth or low birth weight, this is "the first comprehensive review to identify the specific birth defects most associated with smoking," say the authors from University College London.
What's worrisome is that despite the well-known harmful effects of tobacco use, the study found that one in seven women continues to smoke throughout pregnancy in Britain.
The study, which reviewed 172 research papers published over the past 50 years covering 174,000 cases of birth defects, found that for women who smoked while pregnant, the risk of birth defects was increased. Specifically:
- A 50% increased risk of gastroschisis, where parts of the stomach or intestines protrude through the skin.
- A 33% increased risk of skull defects.
- A 28% increased risk of being born with a clubfoot.
- A 28% increased risk of cleft lip or cleft palate.
- A 27% increased risk of gastrointestinal defects.
- A 26% increased risk of missing or deformed limbs.
- A 25% increased risk of eye defects.
- A 10% increased risk of heart defects.
Although it's still unclear how smoking causes these problems, experts believe that the thousands of different toxic chemicals found in cigarette smoke can potentially disrupt fetal development.
"The message from this research is that women should quit smoking before becoming pregnant, or very early on, to reduce the chance of having a baby with a serious and lifelong physical defect," says lead author Professor Allan Hackshaw.
